Cards are a common organizing unit for modern user interfaces (UI). At their core, they’re just rectangular containers with borders and padding. However, when utilized properly to group related information, they help users better digest, engage, and navigate through content. This is why most successful dashboard/UI frameworks make cards a core feature of their component library. This article provides an overview of the API that bslib provides to create Bootstrap cards.
Setup code
To demonstrate that bslib cards work outside of Shiny (i.e., in R Markdown, static HTML, etc), we’ll make repeated use of statically rendered htmlwidgets like plotly and leaflet. Here’s some code to create those widgets:
library(bslib)
library(shiny)
library(htmltools)
library(plotly)
library(leaflet)
plotly_widget <- plot_ly(x = diamonds$cut) %>%
config(displayModeBar = FALSE) %>%
layout(margin = list(t = 0, b = 0, l = 0, r = 0))
leaflet_widget <- leafletOptions(attributionControl = FALSE) %>%
leaflet(options = .) %>%
addTiles()Shiny usage
Cards work equally well in Shiny. In the
examples below, replace plotly_widget with
plotlyOutput() and leaflet_widget with
leafletOutput() to adapt them for Shiny server-rendered
plots/maps.
Hello card()
A card() is designed to handle any number of “known”
card items (e.g., card_header(), card_body(),
etc) as unnamed arguments (i.e., children). As we’ll see shortly,
card() also has some useful named arguments (e.g.,
full_screen, height, etc).
At their core, card() and card items are just an HTML
div() with a special Bootstrap class, so you can use
Bootstrap’s utility classes to customize things like colors,
text, borders,
etc.
card(
card_header(
class = "bg-dark",
"A header"
),
card_body(
markdown("Some text with a [link](https://github.com)")
)
)Some text with a link
Implicit card_body()
If you find yourself using card_body() without changing
any of its defaults, consider dropping it altogether since any direct
children of card() that aren’t “known” card()
items, are wrapped together into an implicit card_body()
call.1
For example, the code to the right generates HTML that is identical to
the previous example:
card(
card_header(
class = "bg-dark",
"A header"
),
markdown("Some text with a [link](https://github.com).")
)Some text with a link.
Restricting growth
By default, a card()’s size grows to accommodate the
size of its contents. Thus, if a card_body() contains a
large amount of text, tables, etc., you may want to specify a
height or max_height. That said, when laying
out multiple cards, it’s likely best not
to specify height on the card(), and instead, let the
layout determine the height layout_column_wrap().
Although scrolling is convenient for reducing the amount of space
required to park lots of content, it can also be a nuisance to the user.
To help reduce the need for scrolling, consider pairing scrolling with
full_screen = TRUE (which adds an icon to expand the card’s
size to the browser window). Notice how, when the card is expanded to
full-screen, max_height/height won’t effect
the full-screen size of the card.
card(
max_height = 250,
full_screen = TRUE,
card_header(
"A long, scrolling, description"
),
lorem::ipsum(paragraphs = 3, sentences = 5)
)Elit libero odio inceptos at nulla, nisi dictumst tempus morbi? Diam a erat nascetur nunc placerat, mi ultrices lacus felis? Enim a diam purus platea felis integer nibh tempor sociis? Nibh non; aenean nisi sapien netus eleifend class vulputate lacinia ac. Na ac.
Dolor tincidunt porttitor cursus tincidunt ante aliquam odio conubia nec quam! Turpis nam curae senectus blandit sodales mauris mollis feugiat nibh. Eleifend pulvinar praesent fringilla parturient, cum tempus consequat: laoreet mi fames, porttitor tempus. Ad tempor, habitasse lobortis vel; viverra laoreet pretium pulvinar curae natoque. Purus dui aptent sapien curae vivamus, quisque iaculis suspendisse.
Elit dui nullam himenaeos placerat rhoncus congue, et ante facilisis odio! Euismod dis mattis phasellus: netus torquent maecenas inceptos pharetra. Iaculis quis ligula vehicula torquent fermentum ligula nibh sodales placerat vestibulum facilisis. Pulvinar tempor mattis sociis luctus suscipit ornare etiam. Na etiam.
Filling outputs
A card()’s default behavior is optimized for
facilitating filling layouts. More
specifically, if a fill item (e.g.,
plotly_widget), appears as a direct child of a
card_body(), it resizes to fit the card()s
specified height. This means, by specifying height = 250
we’ve effectively shrunk the plot’s height from its default of 400 down
to about 200 pixels. And, when expanded to full_screen, the
plot grows to match the card()’s new size.
card(
height = 250,
full_screen = TRUE,
card_header("A filling plot"),
card_body(plotly_widget)
)Most htmlwidgets (e.g., plotly, leaflet, etc) and some other Shiny
output bindings (e.g, plotOutput(),
imageOutput(), etc) are fill items by
default, so this behavior “just works” in those scenarios. And, in some
of these situations, it’s helpful to remove card_body()’s
padding, which can be done via spacing
& alignment utility classes.
card(
height = 275,
full_screen = TRUE,
card_header("A filling map"),
card_body(
class = "p-0",
leaflet_widget
),
card_footer(
class = "fs-6",
"Copyright 2023 RStudio, PBC"
)
)Fill item(s) aren’t limited in how much they grow
and shrink, which can be problematic when a card becomes very small. To
work around this, consider adding a min_height on the
card_body() container. For example, try using the handle on
the lower-right portion of this card example to make the card
taller/smaller.
This interactive example is a bit contrived in that we’re using CSS
resize to demonstrate how to make plots that don’t shrink beyond a
certain point, but this concept becomes quite useful when implementing
page-level filling layouts (i.e.,
page_fillable()) with multiple
cards.
card(
height = 300,
style = "resize:vertical;",
card_header("Plots that grow but don't shrink"),
card_body(
min_height = 250,
plotly_widget,
plotly_widget
)
)Troubleshooting fill
As you’ll learn more about in filling
layouts, a fill item loses its ability to fill when
wrapped in additional UI element that isn’t a fillable
container. To fix the situation, use as_fill_carrier() to
allow the additional element to carry the potential to fill from the
card_body() down to the fill item.
Multiple card_body()
A card() can have multiple card_body()s,
which is especially useful for:
- Combining both resizable and non-resizable contents (i.e., fill items and non-fill).
- Allowing each
card_body()to have their own styling (via inline styles and/or utility classes) and resizing limits (e.g.,min_height).
For example, when pairing filling output with scrolling content, you
may want min_height on the filling output since the
scrolling content will force it to shrink:
card(
height = 375,
full_screen = TRUE,
card_header(
"Filling plot, scrolling description"
),
card_body(
min_height = 200,
plotly_widget
),
card_body(
class = "lead container",
lorem::ipsum(paragraphs = 10, sentences = 5)
)
)Consectetur netus eu sagittis libero nam, et himenaeos rhoncus nullam enim! Urna ultricies, tempus faucibus dictum laoreet per laoreet orci sodales dapibus? Vestibulum scelerisque nec hac pharetra gravida lacinia netus, tellus penatibus. Consequat venenatis luctus etiam leo nisl, diam: neque, dapibus tempor. Na tempor.
Consectetur nibh velit pellentesque vivamus tristique, ad molestie curabitur tristique semper sodales penatibus. Malesuada dignissim nisl, posuere dapibus quam luctus nec, sed viverra conubia? Ultricies placerat tempus cum, varius praesent at netus mus nisi laoreet! Velit augue nisi, aenean et magnis parturient auctor primis, inceptos dignissim lectus lacus! Na lacus.
Consectetur lacus rutrum massa cum felis molestie sociosqu. Parturient posuere scelerisque nunc quisque torquent tempor et neque. Ac mattis et commodo mollis dis mauris nulla massa? Odio ultrices mauris urna. Ad rhoncus nisl viverra integer lectus facilisis, penatibus: laoreet ligula proin blandit sapien ac iaculis sem est tempor felis netus congue purus suspendisse.
Consectetur ornare commodo torquent ut urna blandit lacus lobortis. Molestie scelerisque nam, ad, rutrum cubilia, facilisi nullam dis volutpat fermentum lobortis integer. Non metus pretium ultrices feugiat; dis litora cras dui. Dictum lectus malesuada magnis sodales, vivamus senectus pellentesque metus semper ultricies? Purus lacinia posuere tellus maecenas ultricies sed lacus metus, bibendum ac ullamcorper lobortis sapien mattis aptent auctor aliquam natoque.
Adipiscing pretium imperdiet ligula proin tortor urna proin varius eros. Tristique leo vitae torquent, tortor vivamus massa imperdiet primis. Lacinia ridiculus interdum: eleifend luctus gravida nec velit senectus erat? Ornare dui justo elementum condimentum, volutpat cursus sem, imperdiet est justo. Na justo.
Amet facilisi gravida nisl inceptos malesuada ligula dignissim mauris gravida primis. Scelerisque commodo volutpat tellus iaculis placerat ligula facilisi leo nostra curae neque. Parturient eu sagittis integer facilisi malesuada! Suscipit enim libero lacinia platea ante commodo id! A vel enim aptent curae, primis penatibus sed platea, justo purus rhoncus quis nullam; dis ultricies gravida?
Amet orci imperdiet sociosqu rutrum dignissim vulputate placerat libero, nec, ultrices ridiculus. Tincidunt nisl cursus congue cras sodales curae tortor posuere. Et duis volutpat cras tempor mauris elementum libero neque. Lectus nam tempus magnis ac morbi. Nostra laoreet conubia conubia sodales maecenas, purus non nulla, platea curabitur commodo.
Consectetur conubia risus, semper magnis netus sem lacus, rutrum natoque gravida auctor donec. Tempor nulla; habitasse facilisi fames praesent parturient? Nostra nam vulputate est velit felis, placerat porttitor neque ligula. Porta class hendrerit sapien faucibus varius faucibus erat varius primis dapibus dapibus. Hac nibh consequat taciti aliquet phasellus vivamus: gravida pretium venenatis habitant ullamcorper potenti.
Sit semper convallis euismod facilisi integer hendrerit tempor fermentum. Volutpat habitasse interdum lectus mus luctus euismod ullamcorper leo ad? Leo tincidunt nec eget euismod ornare, fermentum accumsan odio. Gravida felis pulvinar bibendum quis at. Magna pretium vivamus eget; venenatis ornare mi?
Consectetur vestibulum tristique malesuada maecenas odio proin, mi platea parturient. Quisque fusce nostra fusce etiam nisl ullamcorper feugiat! Porta nunc urna imperdiet, cras metus id, dignissim, vivamus facilisi bibendum dictumst lacus interdum. Curae magnis fringilla, porta etiam rutrum aenean quam vestibulum leo. Eleifend proin dapibus fames dis tortor tellus elementum cubilia.
Also, when the content has a fixed size, and should not be allowed to
scroll, set fill = FALSE:
card(
height = 350,
full_screen = TRUE,
card_header(
"Filling plot, short description"
),
plotly_widget,
card_body(
fill = FALSE, gap = 0,
card_title("A subtitle"),
p(class = "text-muted", "And a caption")
)
)A subtitle
And a caption
Multiple columns
As you’ll learn in column-based
layouts, layout_column_wrap() is great for multi-column
layouts that are responsive and accommodate for filling output. Here we have an equal-width
2-column layout using width = 1/2, but it’s also possible
to have varying column
widths.
card(
height = 350,
full_screen = TRUE,
card_header("A multi-column filling layout"),
card_body(
min_height = 200,
layout_column_wrap(
width = 1/2,
plotOutput("p1"),
plotOutput("p2")
)
),
lorem::ipsum(paragraphs = 3, sentences = 5)
)Amet fermentum facilisis elementum phasellus, cubilia gravida ornare, platea eros. Ante convallis dictum congue etiam eros tellus metus porttitor est quam cum nam? Ornare tortor nec nascetur nullam phasellus tortor tristique congue venenatis mus dapibus! Class lacus lacinia fames urna augue, inceptos scelerisque nunc! Faucibus non nunc aenean et, laoreet potenti suspendisse dis blandit.
Adipiscing fringilla aliquam pulvinar hendrerit suscipit condimentum. Ad per consequat curae accumsan eu penatibus porttitor urna. Aliquet mus platea eleifend rutrum dictumst tortor vel varius orci scelerisque. Taciti maecenas non id, sollicitudin aliquam semper cras. Magna suscipit cras dui auctor sagittis, molestie, semper sociosqu, porttitor duis: vestibulum nulla venenatis donec vivamus leo sed.
Amet metus lobortis duis mollis tellus varius. Mollis faucibus, neque pharetra – class orci vestibulum ornare! Dapibus urna at vestibulum suspendisse et sociis nulla malesuada maecenas nunc. Id volutpat fames dictumst in rhoncus magna mi scelerisque suscipit. Rhoncus natoque euismod nullam dictumst lacinia, lobortis, porttitor feugiat – fames dapibus lobortis lobortis placerat vivamus ultrices?
Multiple cards
layout_column_wrap() is especially nice for laying out
multiple cards since each card in a particular row will have the same
height (by default). Learn more in column-based layouts.
layout_column_wrap(
width = 1/2,
height = 300,
card(full_screen = TRUE, card_header("A filling plot"), plotly_widget),
card(full_screen = TRUE, card_header("A filling map"), card_body(class = "p-0", leaflet_widget))
)Multiple tabs
navset_card_tab() and navset_card_pill()
make it possible to create cards with multiple tabs or pills. These
functions have the same full_screen capabilities as normal
card()s as well some other options like title
(since there is no natural place for a card_header() to be
used). Note that, each nav_panel() object is similar to a
card(). That is, if the direct children aren’t already card
items (e.g., card_title()), they get implicitly wrapped in a
card_body().
library(leaflet)
navset_card_tab(
height = 450,
full_screen = TRUE,
title = "HTML Widgets",
nav_panel(
"Plotly",
card_title("A plotly plot"),
plotly_widget
),
nav_panel(
"Leaflet",
card_title("A leaflet plot"),
leaflet_widget
),
nav_panel(
shiny::icon("circle-info"),
markdown("Learn more about [htmlwidgets](http://www.htmlwidgets.org/)")
)
)Sidebars
As you’ll learn more about in sidebar
layouts, layout_sidebar() just works when placed inside
in a card(). In this case, if you want fill
items (e.g., plotly_widget) to still fill the card
like we’ve seen before, you’ll need to
set fillable = TRUE in layout_sidebar().
card(
height = 300,
full_screen = TRUE,
card_header("A sidebar layout inside a card"),
layout_sidebar(
fillable = TRUE,
sidebar = sidebar(
actionButton("btn", "A button")
),
plotly_widget
)
)Static images
card_image() makes it easy to embed static (i.e.,
pre-generated) images into a card. Provide a URL to href to
make it clickable. In the case of multiple card_image()s,
consider laying them out in multiple cards
with layout_column_wrap() to produce a grid of clickable
thumbnails.
card(
height = 300,
full_screen = TRUE,
card_image(
file = "shiny-hex.svg",
href = "https://github.com/rstudio/shiny"
),
card_body(
fill = FALSE,
card_title("Shiny for R"),
p(
class = "fw-light text-muted",
"Brought to you by RStudio."
)
)
)Flexbox
Both card() and card_body() default to
fillable = TRUE (that is, they are CSS flexbox
containers), which works wonders for facilitating filling outputs, but it also leads to
surprising behavior with inline tags (e.g., actionButton(),
span(), strings, etc). Specifically, each inline tag is
placed on a new line, but in a “normal” layout flow
(fillable = FALSE), inline tags render inline.
card(
card_body(
fillable = TRUE,
"Here's some", tags$i("inline"), "text",
actionButton("btn1", "A button")
),
card_body(
fillable = FALSE,
"Here's some", tags$i("inline"), "text",
actionButton("btn2", "A button")
)
)That said, sometimes working in a flexbox layout is quite useful,
even when working with inline tags. Here we leverage flexbox’s gap
property to control the spacing between a plot, a (full-width) button,
and paragraph. Note that, by using markdown() for the
paragraph, it wraps the results in a <p> tag, which
means the contents of the paragraph are not longer subject to
flexbox layout. If we wanted, we could do something similar to render
the actionButton() inline by wrapping it in a
div().
card(
height = 325, full_screen = TRUE,
card_header("A plot with an action links"),
card_body(
class = "gap-2 container",
plotly_widget,
actionButton(
"go_btn", "Action button",
class = "btn-primary rounded-0"
),
markdown("Here's a _simple_ [hyperlink](https://www.google.com/).")
)
)In addition to gap, flexbox has really nice ways of handling otherwise difficult spacing and alignment issues. And, thanks to Bootstrap’s flex utility classes, we can easily opt-in and customize defaults.
card(
height = 300, full_screen = TRUE,
card_header(
class = "d-flex justify-content-between",
"Centered plot",
checkboxInput("check", " Check me", TRUE)
),
card_body(
class = "align-items-center",
plotOutput("id", width = "75%")
)
)Shiny
Since this article is statically rendered, the examples here use
statically rendered content/widgets, but the same card()
functionality works for dynamically rendered content via Shiny (e.g.,
plotOutput(), plotlyOutput(), etc).
An additional benefit that comes with using shiny is the ability to
use getCurrentOutputInfo() to render new/different content
when the output container becomes large enough, which is particularly
useful with card(full_screen = T, ...). For example, you
may want additional captions/labels when a plot is large, additional
controls on a table, etc (see the value
boxes article for a clever use of this).
# UI logic
ui <- page_fluid(
card(
max_height = 200,
full_screen = TRUE,
card_header("A dynamically rendered plot"),
plotOutput("plot_id")
)
)
# Server logic
server <- function(input, output, session) {
output$plot_id <- renderPlot({
info <- getCurrentOutputInfo()
if (info$height() > 600) {
# code for "large" plot
} else {
# code for "small" plot
}
})
}
shinyApp(ui, server)Appendix
The following CSS is used to give plotOutput() a
background color; it’s necessary here because this documentation page is
not actually hooked up to a Shiny app, so we can’t show a real plot.